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What would the SPF (sun protection factor) be for window film, using the same scale used by the sun screen manufacturers?

April 26, 2017Factor Film manufacturers scale screen SPF Sun Used window

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What would the SPF (sun protection factor) be for window film, using the same scale used by the sun screen manufacturers?

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Since an SPF 15 allows you to stay in the sun without burning fifteen times longer than you could if you didn’t use any sunscreen, the calculation of the SPF for window film is fairly easy. The number is very large indeed. If the film product allows less than 1% UV transmission, the SPF would be about 100 or more. With 1.5% UV transmission, the SPF is 66.66. With a UV transmission of 2%, the SPF would be 50, etc. Simply divide 100 by the percentage of UV transmission. Make sure that your UV transmission number covers the whole range of UVA and UVB radiation. NOTICE: While this computation is easy to perform, it must be said that most dermatologists don’t think numbers larger than about 20 are meaningful. Moreover, these SPF numbers are officially determined by actual skin testing according to an established experimental protocol. It is not permissible to make such claims about actual SPF numbers without having these skin tests performed by a qualified laboratory.